ArrayIndexOutOfBoundsException = 0

Question

Got DBTableHeaderFill Error: ArrayIndexOutOfBoundsException = 0

想不通，为什么会出现...

col 是 11 因为 table 有 12 headers，我们知道计数从 0

开始

我知道它看起来很原始，但我只是在调试问题... JOptionPane 用于查看哪些有效，哪些无效，我不知道数组有什么问题...

    Object rows[][] = new Object[row][col];
    Object columns [] = new Object[col];
    row = 1;
    col = 11;
    JTable table = new JTable(rows, columns);
    scrollPane.setViewportView(table);
    /*
     *  DataBase Headers
     */
    try{
        conn = DBConnection.DBConnector();
        JOptionPane.showMessageDialog(null, "Connection");
        Statement st = conn.createStatement();
        JOptionPane.showMessageDialog(null, "Statement");
        rs = st.executeQuery("SELECT * FROM Query1");
        JOptionPane.showMessageDialog(null, "Query1 load");
        ResultSetMetaData rsmd = rs.getMetaData();
        JOptionPane.showMessageDialog(null, rsmd);
        int columnCount = rsmd.getColumnCount();
        JOptionPane.showMessageDialog(null, columnCount);
        JOptionPane.showMessageDialog(null, "test " + col);
        // The column count starts from 0
        for (int i = 1; i < columnCount + 1; i++ ) {
            columns[i-1] = rsmd.getColumnName(i);
            JOptionPane.showMessageDialog(null, "result: " + o);
            JOptionPane.showMessageDialog(null, "Header" + columns[i-1]);
          // Writes headers
        }
    }catch(Exception e){
        JOptionPane.showMessageDialog(null, "DBTableHeaderFill Error: " + e);
    }

当我在数组之前分配 col 和 row 值时，出现以下错误：

java.lang.NullPointerException at javax.swing.JTable.getColumnName(Unknown Source) at javax.swing.JTable.addColumn(Unknown Source) at javax.swing.JTable.createDefaultColumnsFromModel(Unknown Source) at javax.swing.JTable.tableChanged(Unknown Source) at javax.swing.JTable.setModel(Unknown Source) at javax.swing.JTable.(Unknown Source) at javax.swing.JTable.(Unknown Source) at javax.swing.JTable.(Unknown Source) at Main.initialize(Main.java:199) at Main.(Main.java:65) at Main.run(Main.java:34) at java.awt.event.InvocationEvent.dispatch(Unknown Source) at java.awt.EventQueue.dispatchEventImpl(Unknown Source) at java.awt.EventQueue.access0(Unknown Source) at java.awt.EventQueue.run(Unknown Source) at java.awt.EventQueue.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source)

所以我发现了我的问题...

JTable table = new JTable(rows, columns);
scrollPane.setViewportView(table);

这需要在数组的末尾....

Answer 1

变量col设置在：

之后

Object columns [] = new Object[col];

这一行之前的 col 值是多少？如果它是 0，那么这将解释你得到的错误：

Got DBTableHeaderFill Error: ArrayIndexOutOfBoundsException = 0

Answer 2

您似乎在使用 row/col 值创建数组后初始化它们：

Object rows[][] = new Object[row][col];
Object columns [] = new Object[col];
row = 1;
col = 11;

这应该是：

row = 1;
col = 11;
Object rows[][] = new Object[row][col];
Object columns [] = new Object[col];

并且 col 应该是您的 table 具有的确切列数，否则您将创建一个只有 11 个元素长的数组，而不是 12 个元素。

ArrayIndexOutOfBoundsException = 0

ArrayIndexOutOfBoundsException = 0

java

jtable